GLUT2 (glucose transporter) homotetramers associated with the plasma membrane mediate the facilitated diffusion of glucose between the cytosol and the extracellular space, so glucose will leave cells when its intracellular concentration exceeds the extracellular one (Colville et al. 1993; Santer et al. 1997; Wu et al. 1998). In the body, such glucose export is a normal feature of liver cells when gluconeogenesis or glycogen breakdown is underway.